The present invention relates to apparatus for handling webs of material and, more particularly, apparatus for collating a plurality of webs of material, forming regularly spaced cross perforations on the collated webs, and folding the perforated webs at the perforations.
A recurring problem with such collators is the synchronization of the various units performing the successive operations, particularly in producing business forms. This type of apparatus includes a collating unit in which a plurality of webs of material are unwound from rolls and are glued or otherwise attached to each other in overlapping relation to make continuous forms.
The collated webs are conveyed to a cross perforating unit and passed between a pair of driven cylinders or rolls, one of which is fitted with transverse perforating knives. The perforating roll typically includes a single pair of knives placed at diametrically opposite positions about its circumference, and the rolls are sized such that the circumferential distance between the knives equals the desired spacing between successive cross perforations on the collated webs. After passing between the rolls, the collated web enters a folding unit which folds the web at the transverse rows of perforations and forms a vertical, fan-folded stack.
In order to minimize the materials and labor costs involved in constructing such devices, it is desirable to drive all of the units from a single source. Typically, a variable speed electric motor rotates a main drive gear which is connected to and drives the collator, perforator and folder units by a series of intermeshing gears and pulley and timing belt combinations. As a result of the manufacturing tolerances for the gears used in these devices, the bore in such a gear which receives the mounting shaft is slightly offset from the center of the gear. The periphery or pitch circle of the gear will then have a geometric center which is spaced slightly from the center of rotation of the shaft upon which the gear is mounted, thereby introducing an eccentricity into the rotation of that gear.
In some instances, the eccentricities of gears in a gear train are oriented in substantially the same phase relative to each other so that they become additive and the resultant eccentricity of the gear train noticeably effects the synchronization of a particular unit relative to the other units of the apparatus. Most commonly, a large resultant eccentricity in a gear train causes the linear speed of the collated webs entering the perforator to vary relative to the speed at which the perforating cylinders rotate. Conversely, a large resultant eccentricity may affect the performance of the perforator such that the perforating knives do not rotate at a constant tangential speed.
The result for either deviation is a cyclical variance in the spacing between transverse rows of perforations. This results in the formation of stacks having folded sheets of a cyclically varying length so that a column of such sheets has a perceptible sinusoidal shape on its front and rear sides formed by rows of overlying perforations. Such a stack is undesirable not only from an aesthetic standpoint, but from a practical standpoint in that such stacks of folded sheets are often difficult or impossible to load into a box dimensioned to receive a column of sheets having a relatively nonvarying length.
Attempts have been made to eliminate or compensate for the eccentricities inherent in the gears of gear trains in such collating apparatus. For example, a common practice is to reposition selected gears at random relative to other gears in the gear train with the goal of orienting the repositioned gears such their eccentricities are out of phase with the eccentricities of the other gears and, therefore, would cancel them. This method is extremely time-consuming and, since the eccentricities are not visually perceptible, the proper selection and positioning of gears is left to chance.
Another attempted solution to this problem is to provide gear trains with a relatively large number of meshing gears so the large number of individual gear eccentricities, when added together, will substantially cancel each other and the components of the apparatus are sufficiently synchronous to provide an acceptable stack of folded sheets. The disadvantage with this solution is that there is no assurance of a successful arrangement of gears, and the inclusion of such a large number of gears increases the cost of manufacturing and maintaining such apparatus.
A different solution is described in the Loase U.S. Pat. No. 3,369,436, issued Feb. 20, 1968, to the assignee of this application. That patent discloses an apparatus for processing a web of material which includes a pair of perforating rolls in which an upper roll includes an adjustable gear mounted on its supporting axle. The adjustable gear includes a hub which receives the axle through an eccentric bore and an outer gear ring which receives the hub through an eccentric bore.
The gear ring and hub are adjustable relative to each other such that an eccentricity of predetermined magnitude may be introduced into the rotation of that gear to compensate for eccentricities in other gears with which it meshes so that the rotational speed of the perforating roll to which it is attached matches the varying linear speed of the web which it engages. A disadvantage with such a gear is that it is keyed onto the axle on which it is mounted and lacks means for changing the phase of that gear to compensate for eccentricities having different phases.
Accordingly, there is a need for a collating apparatus in which the various units can be synchronized to compensate for eccentricities occurring in the gears driving the units to eliminate sinusoidal or cyclical variations in the finished stack of forms. Such a collating apparatus should be capable of on-site adjustment to eliminate such asynchronous operation of units, and the means of adjustment should be relatively simple and economical to operate.